This invention relates to a process for the production of triazolone compounds. More particularly, the invention relates to a process for the production of 1,2,4-triazol-5-one from semicarbazide compounds.
1,2,4-Triazol-5-one (or its tautomeric form; 5-hydroxy-1H-l,2,4-triazole) is a known compound useful as an intermediate in the production of explosives and in the synthesis of dyestuffs.
The preparation of 1,2,4-triazol-5-one has been reported by a number of investigators. C. Runti et al [Ann. Chim. (Rome) 49, 1649-1667, 1959: Chem. Abstracts 54,22602k (1960)] refluxed semicarbazide.HCl with ethyl orthoformate for one hour, the reaction mixture cooled, filtered, and crystallized from ethanol to give 1,2,4-triazol-5-one.
C. F. Kroeger et al prepared 4-amino-l,2,4-triazol-5-one by heating carbohydrazide and ethylorthoformate on a water bath. The amino derivative was deaminated by treatment with NaNO.sub.2 in HCl and neutralized with NaOH [Chem. Ber. 98 (9) 3025-3033 (1965); Chem. Abstracts 63,16339g (1965)].
1,2,4-Triazol-5-one was prepared by G. I. Chipen et al by several methods including the reaction of formic acid with acetone semicarbazone and with semicarbazide.HCl, the latter method being considered optimal. Semicarbazide.HCl and 85 percent formic acid were boiled for 8 hours and kept for 12 hours at 0.degree.C. to prepare of 1,2,4-triazol-5-one. [Khim. Geterotsikl. Soed: 2 (1) 110-116 (1966); Chem. Abstracts 65,705b (1966)].
M. Dobosz prepared 1,2,4-triazol-5-one by the reaction of triformylaminomethane with semicarbazide or its hydrochloride as reported in Ann. Univ. Mariae Curie-Sklodowska, Sect. AA: Chem. 34, 163 (1979), Chem. Abstracts 100, 34468, (1984).
The preparations recorded in the prior art give 1,2,4-triazol-5-one in low yields or where semicarbazide.HCl is a reactant, the product contains high concentrations of chloride ions. In an important application, the triazolone compound is nitrated to produce 3-nitro-l,2,4-triazol-5-one which is used in cast explosive compositions. It is known that the presence of high chloride concentrations in castable explosives stored, for example, in metal casings results in increased corrosion of the casings and increased gas formation.
In addition, 1,2,4-triazol-5-one having high concentrations of chloride ion can undergo undesired chemical reactions. For example, Kroeger et al (op. cit.) found that when 3-nitro-l,2,4-triazol-5-one was heated with hydrochloric acid, chloro-denitration resulted and 3-chloro-l,2,4-triazol-5-one was formed in 87 percent yield.
Therefore, there is a need for a process for producing 1,2,4-triazol-5-one having reduced concentrations of impurities such as chlorides.